Plan your installation

Estimated reading time: 9 minutes

This topic applies to Docker Enterprise.

The Docker Enterprise platform business, including products, customers, and employees, has been acquired by Mirantis, inc., effective 13-November-2019. For more information on the acquisition and how it may affect you and your business, refer to the Docker Enterprise Customer FAQ.

Docker Universal Control Plane helps you manage your container cluster from a centralized place. This article explains what you need to consider before deploying Docker Universal Control Plane for production.

System requirements

Before installing UCP, make sure that all nodes (physical or virtual machines) that you’ll manage with UCP:

Hostname strategy

Docker UCP requires Docker Enterprise. Before installing Docker Enterprise on your cluster nodes, you should plan for a common hostname strategy.

Decide if you want to use short hostnames, like engine01, or Fully Qualified Domain Names (FQDN), like Whichever you choose, confirm your naming strategy is consistent across the cluster, because Docker Engine and UCP use hostnames.

For example, if your cluster has three hosts, you can name them:

Static IP addresses

Docker UCP requires each node on the cluster to have a static IPv4 address. Before installing UCP, ensure your network and nodes are configured to support this.

Avoid IP range conflicts

The following table lists recommendations to avoid IP range conflicts.

Component Subnet Range Default IP address
Engine fixed-cidr CIDR range for docker0 interface and local containers
Engine default-address-pools CIDR range for docker_gwbridge interface and bridge networks
Swarm default-addr-pool CIDR range for Swarm overlay networks
Kubernetes pod-cidr CIDR range for Kubernetes pods
Kubernetes service-cluster-ip-range CIDR range for Kubernetes services


There are two IP ranges used by the engine for the docker0 and docker_gwbridge interface:


By default, the Docker engine creates and configures the host system with a network interface called docker0, which is an ethernet bridge device. If you don’t specify a different network when starting a container, the container is connected to the bridge and all traffic coming from and going to the container flows over the bridge to the Docker engine, which handles routing on behalf of the container.

Docker engine creates docker0 with a configurable IP range. Containers which are connected to the default bridge are allocated IP addresses within this range. Certain default settings apply to docker unless you specify otherwise. The default subnet for docker0 is

The recommended way to configure the docker0 settings is to use the daemon.json file. You can specify one or more of the following settings to configure the docker0 interface:

  "bip": "",
  "fixed-cidr": "",

bip: Supply a specific bridge IP range for the docker0 interface, using standard CIDR notation. Default is

fixed-cidr: Restrict the IP range for docker0, using standard CIDR notation. Default is This range must be an IPv4 range for fixed IPs, and must be a subset of the bridge IP range (bip in daemon.json). For example, with, IPs for your containers will be chosen from the first half of addresses( - included in the bip( subnet.


The docker_gwbridge is a virtual bridge that connects the overlay networks (including the ingress network) to an individual Docker engine’s physical network. Docker creates it automatically when you initialize a swarm or join a Docker host to a swarm, but it is not a Docker device. It exists in the kernel of the Docker host. The default subnet for docker_gwbridge is


If you need to customize the docker_gwbridge settings, you must do so before joining the host to the swarm, or after temporarily removing the host from the swarm.

The recommended way to configure the docker_gwbridge settings is to use the daemon.json file. You can specify one or more of the following settings to configure the interface:

     "default-address-pools": [

default-address-pools: A list of IP address pools for local bridge networks, the default is a single pool {"base":"","size":24}. This allocates /24 network from the CIDR range for local bridge networks. Each entry in the list contain the following:

base: CIDR range to be divided up for bridge networks, the default is

size: CIDR netmask that determines the default network size to allocate from the base pool, the default is 24


Swarm uses a default address pool of for its overlay networks. If this conflicts with your current network implementation, please use a custom IP address pool. To specify a custom IP address pool, use the --default-addr-pool command line option during Swarm initialization.


The Swarm default-addr-pool setting is separate from the Docker engine default-address-pools setting. They are two separate ranges that are used for different purposes.


Currently, the UCP installation process does not support this flag. To deploy with a custom IP pool, Swarm must first be initialized using this flag and UCP must be installed on top of it.


There are two internal IP ranges used within Kubernetes that may overlap and conflict with the underlying infrastructure:

  • The Pod Network - Each Pod in Kubernetes is given an IP address from either the Calico or Azure IPAM services. In a default installation Pods are given IP addresses on the range. This can be customized at install time by passing the --pod-cidr flag to the UCP install command.
  • The Services Network - When a user exposes a Service in Kubernetes it is accessible via a VIP, this VIP comes from a Cluster IP Range. By default on UCP this range is Beginning with 3.1.8, this value can be changed at install time with the --service-cluster-ip-range flag.

Avoid firewall conflicts

For SUSE Linux Enterprise Server 12 SP2 (SLES12), the FW_LO_NOTRACK flag is turned on by default in the openSUSE firewall. This speeds up packet processing on the loopback interface, and breaks certain firewall setups that need to redirect outgoing packets via custom rules on the local machine.

To turn off the FW_LO_NOTRACK option, edit the /etc/sysconfig/SuSEfirewall2 file and set FW_LO_NOTRACK="no". Save the file and restart the firewall or reboot.

For SUSE Linux Enterprise Server 12 SP3, the default value for FW_LO_NOTRACK was changed to no.

For Red Hat Enterprise Linux (RHEL) 8, if firewalld is running and FirewallBackend=nftables is set in /etc/firewalld/firewalld.conf, change this to FirewallBackend=iptables, or you can explicitly run the following commands to allow traffic to enter the default bridge (docker0) network:

firewall-cmd --permanent --zone=trusted --add-interface=docker0
firewall-cmd --reload

Time synchronization

In distributed systems like Docker UCP, time synchronization is critical to ensure proper operation. As a best practice to ensure consistency between the engines in a UCP cluster, all engines should regularly synchronize time with a Network Time Protocol (NTP) server. If a host node’s clock is skewed, unexpected behavior may cause poor performance or even failures.

Load balancing strategy

Docker UCP doesn’t include a load balancer. You can configure your own load balancer to balance user requests across all manager nodes.

If you plan to use a load balancer, you need to decide whether you’ll add the nodes to the load balancer using their IP addresses or their FQDNs. Whichever you choose, be consistent across nodes. When this is decided, take note of all IPs or FQDNs before starting the installation.

Learn how to set up your load balancer.

Load balancing UCP and DTR

By default, UCP and DTR both use port 443. If you plan on deploying UCP and DTR, your load balancer needs to distinguish traffic between the two by IP address or port number.

  • If you want to configure your load balancer to listen on port 443:
    • Use one load balancer for UCP and another for DTR.
    • Use the same load balancer with multiple virtual IPs.
  • Configure your load balancer to expose UCP or DTR on a port other than 443.

If you want to install UCP in a high-availability configuration that uses a load balancer in front of your UCP controllers, include the appropriate IP address and FQDN of the load balancer’s VIP by using one or more --san flags in the UCP install command or when you’re asked for additional SANs in interactive mode. Learn about high availability.

Use an external Certificate Authority

You can customize UCP to use certificates signed by an external Certificate Authority. When using your own certificates, you need to have a certificate bundle that has:

  • A ca.pem file with the root CA public certificate,
  • A cert.pem file with the server certificate and any intermediate CA public certificates. This certificate should also have SANs for all addresses used to reach the UCP manager,
  • A key.pem file with server private key.

You can have a certificate for each manager, with a common SAN. For example, on a three-node cluster, you can have:

  • with SAN
  • with SAN
  • with SAN

You can also install UCP with a single externally-signed certificate for all managers, rather than one for each manager node. In this case, the certificate files are copied automatically to any new manager nodes joining the cluster or being promoted to a manager role.

Where to go next

UCP, install, Docker EE